Advancements in vitreoretinal surgical techniques will lead to more reliable means of treating vision threatening vitreoretinal disorders such as proliferative diabetic retinopathy, giant retinal tears, penetrating ocular trauma and retinal detachments complicated by proliferative vitreoretinopathy. The surgical management of these conditions can be critically dependent on the use of gaseous or liquid substances which maintain neural retina in apposition to retinal pigment epithelium postoperatively. Currently used materials have drawbacks that limit their usefulness in some cases. Alternatively, hydrophilic polymers composed of a synthetic nonbiodegradable carbon/carbon backbone have several features which make them ideal for this purpose. The objective of the proposed work is to investigate both the usefulness and safety of these materials when placed within the vitreous cavity in conjunction with vitreoretinal surgery. These studies will involve the investigation of a) a linear hydrophilic polymer of acrylamide and b) a three dimensional copolymer (hydrogel) of polyacrylonitrile. Ocular tolerance to placement of hydrophilic polymer in the vitreous cavity will be evaluated in rabbits and pigs. By indirect ophthalmoscopy and slit lamp examination in the rabbit, an assessment will be made of the optical clarity of the intravitreally injected material and of the retention of lens and corneal transparency. An inflammatory response in the vitreous cavity, if present, would also be detected during these examinations. Intraocular pressure will also be monitored. These experiments in the rabbit will include an electroretinographic assessment of retinal function and light and electron microscopic study of retinal morphology. The compatibility of these materials for use in the vitreous cavity will also be revealed in rabbits by fluorophotometric measurements of the blood-ocular barriers. In porcine eyes, tolerance will be evaluated by indirect ophthalmoscopy and light and electron microscopic analysis of retina. Experiments will also demonstrate the benefits of using intravitreally injected hydrophilic polymer in conjunction with vitreoretinal surgery. Firstly, fluorophotometric studies in rabbits will be employed to determine whether the maintenance or recovery of blood-retinal and blood- aqueous barrier integrity following vitrectomy surgery is influenced by intravitreal placement of hydrophilic polymer. The latter studies will involve the use of a linear polymer of polyacrylamide. Secondly, the value of an intravitreally placed hydrogel in maintaining retinal reapposition following retinal reattachment surgery will be established using cat retina as an experimental model for retinal detachment.